Aromatic carbonates such as diphenyl carbonate (DPC) are common reagents in the formation of polycarbonates. One of the most important processes to prepare DPC is the transesterification of a dialkyl carbonate. For example the transesterification of diethyl carbonate and phenol to form intermediate phenylethyl carbonate which can then be subjected to another transesterification with phenol or a disproportionation reaction to DPC. Another example is the transesterification of (I) dimethyl carbonate (DMC) and phenol (PhOH) to form intermediate phenyl methyl carbonate (PMC) which can then be subjected to another transesterification with phenol (II) or a disproportionation reaction (III) to DPC as shown in the following schemes.

Homogeneous catalysts are known to be used in the transesterification of aromatic hydroxy compounds (also referred to as aromatic alcohols) and dialkyl carbonates to produce aromatic carbonates. These catalysts are corrosive and need to be dissolved in the reactants. Additionally, these catalysts have to be separated from the reactor effluent before further processing of the final product. Although a large portion of the homogeneous catalyst can be recycled, a certain amount of fresh catalyst must be supplied continuously to the reaction system for an industrial process. This results in a complicated and energy intensive industrial process. In addition, trace amounts of homogeneous catalyst ending up in the product affects the properties of the resulting polymeric material rendering it unsuitable for certain applications.
There have been a few reports of heterogeneous transesterification catalysts, although their activity and selectivity are not high enough to be attractive for industrial application.
There remains a need in the art for new transesterification catalysts that are improved above the known homogeneous catalysts and the heterogeneous catalysts, particularly in activity and selectivity.